Pulpstone



Aug. 24, 1948. 2,447,943

G. N. JEPPSON PULPSTONE 2 Sheets-Sheet 1 Filed Oct. 50, 1945 Aug. 24,1948.

G. N. JEPPSON PULPSTONE 2 Sheets-Sheet 2 Filed 001:. 30, 1945 GEORGE N.IJEPF'SUN I3 20 IO I5 26 repaired.

Patented Aug. 24, 1948 UNITED v, 1 STATES PATENT 2,447,943 runrs'ronnGeor e N. Jeppson, Worcester, Mass; assignor to Norton Company,Worcester, Mas's., a corporation of Massachusetts J i 1KppIicationOctobei-SO,1945, Serial I 7 Claims. 01.51 296) a a l t Theinvention relates to pulpstones;

One object of the invention is to provide a strong pulpstone. Anotherobject of the invention is to provide a pulpstonejwhichcan be easilyAnother object a the invention isto provide such a construction in whichthe portions of the block which are held by the bolts are under compression. Another object of the invention is to provide a'sizeablesurface of the block engaged by ail-clamping bolt or a washer thereon.

"Another object of the invention is: to provide a; construction havingone or more of the characteris'tics indicated with clear-ance forrelative moyem'entbetween the blocks and the bolts inacircumferentialdirection of the stone. Other objects will be in partobvious or in part pointed out hereinafter. i w 'The inventionaccordingly consists inthe features of construction, combinations ofelements, arrangements of parts, and in the severalsteps and relationand order of each of said steps to one or more of the others thereof,all as will be illustratively described herein, and'the scope of theapplication of which will be indicated in the following claims. I 'Inthe accompanying drawings in which is shown one of many possibleembodiments of the mechanical features of this invention.

Figure 1 is a sectional view in aplane perpendice ular'tothe axis of apulpstone constructed in accordance with theinvention;

Figure 2 is a. perspective view of an abrasive insert which is used whena broken block is replaced with a new block;

"Figure 3 is a viewer a single pulpstone block from the inner sidethereof; Figure 4 is a view of'a fragment of the stone inthe samesection as'sho'wn in Figure 1 but on an enlarged scale; I i k fFigure 5is asectional'viewin anaxial plane taken along'the line 5-5 of Figure 4;

--Figure 6' is a fragmentary sectional-view, on a further enlarged scaletaken along the line 5-6 of Figure 4. u I f Referring first to Figure 1the pulps-tone comprises a plurality of bonded abrasive blocks l0 and a,central concrete core ll.

body of abrasive blocks with an outer surf-ace of revolution; While inmost cases this outer surface of revolution will be a cylinder it iscontemplated that other surfaces may Deformed, such as cones, ellipsoidsand paraboloids. While the invention'principally relates to' pulpstbnes,

The blocks III" are arranged in circular rows to forma hollow it inay beembodied in stories for pulpirefining en E- gines or for any otherpurpose,

The blocks!!! may be made'of ny suitable abrasiveYsuch as silicon.carbide o r-"aluminum" oxide, bonded by any suitable, bond, vitrifiedbond being preferred. Other bonds' such'fas p asma; formaldehyderesin,'rubbr; shellac, ma nesium; city-chloride or metal; bond mayfb esdwrm manufacture :of the bonded abrasive is 'l t novvin and hence neednot furtherlbe described3 herein. v I

- Between blocks .IU of the pulpstone is incorpo rated filler. materialIt "preferablyat all facesi ofithe blocks which would otherwisebeinjon-j tact witha face or faces of another block. Since; sujch fillermaterial I 2 mlay have nofabrasivei properties, it is 'desirabletois"arrange' the blocks that therewill beno truecircleont'he surface? ofthe'stone entirely along the fillermaterial' 'IZ.

Thisma'y be ,done in: several different ways, such? as, by shaping thest or es tomake'j zigzag joints such as shown'in'patent to Lai $$Q i NOJ1 4551 The filler material l2 may be ofany desired type" but preferablyis a material whichadl' eres to the faces'gf the blocks l 0 and has somestrength "but which will deiorm in response to excessive Qcircumferential and axial forces, such as, caused by overheating of the,stone Iprefer'the iillerj material such as described in patent to'Lars'sorr N6. 2,054371 and I have found that the use ofsyntheticru'bb'er actually improves the'quality; o'ffthisniateriall Asdescribed inv the Larsson' patent the filler material is: rubbercontaining enoughsulphur ,to vulcanize to a hard rubb' together withgranules offcork interspersed the in to form collapsible pockets. u

' "Referring now to Figure 3 in connection with Figure}, each block it!may-have'an outerjsu'rface i3 in theshap'e of a segment ofa cylinder orcone etc; an inner surface 14 which "is flat except for a'plurality ofgrooves I5; apair of side surfaces;

small dihedral angles'with radial planes ofjthe stoneperpendicular tothe'a xisl' shownin Figures 4, 5 and grooves 21- 2! extending from theface 14 to; pock'ets'ill. The bottoms of the pockets-20 forrrij 6,eac hstone I'D has washers"2 5in the pockets Zllseated on thseatsj nuts 30are tightened to put a pre-tension on 910 the bolts 26 sufficient tohold the blocks l [I to the .core ll against all forces tending toremove -tii blocks I9 from the center It. E'noughpre-ten even whensubjected to destructive forces will not move from the support H untilthe abrasive it- I self gives away.

After the required number of blocks [B have thus been provided with-bars23, bolts 26, washers 25, washers 29 and nuts 30, they are built upintov an annulus with sheets of material l2. between them; {Iheannulusisthen securely clamped together :by circumferential clamps and theentire structure is then placed in an oven and heated to around '1'6. 0lcentigr ade, for a periodof about 24 hours to vulcaniz'e thematerial T2.plurality of concentr'ic steel cagesconiprising steel hoopsifispacedapart by steel or iron spacing members, notare-'thenpl'acedinside the annulus of ,blocksin thefposition indic'atedinthe drawings. As illustrated in Figureb the hoops 35 of thetwo outercages. canbeplaced between bolts 23. Thisentire assembly is mounted uponthe bottomplate of a mold and a pair-6f iron or steel moldfs-leeves arethen placed in the center thereofl, The molding equipment is not shownas it isgnow well known in; the art and 'forms no part o'f the finalarticle.- Concrete consisting of Portland-c'eriient with sand and aSui-table; amount of trap-rock is then poured into .place'between themold sleeves and the annulus of the'blocks 1 0 and allowedto set I l hepulpstone c'onstr'uctet i as above described is wellable -to res'ist.mechanical stress'sand heat shock. Each block lfl'iissecurely clampedtoa pair o'fluba'rs:23 whichfare preferably made of steel. I arge.pertions,of each block l0 (under the shoulders?!) are -undercompression. iYet no tightenthe of anythingv isnecessary after theannulus i s' -bui ltup. The blooks l'D are'keyed to the concrete centerIt because concretev flows into, the grooves 15 and for-mskeys.Thesekeys drive the blocks; incases of circumferential expansion of theblocks, the deformable material "l2 provides the-saietyvalve, andthis-same ma'terial serves to prevent the breakdown of therear (inrelation warrants ofirot'atibn'). edges ofI the block-s.

It is almost certain that the bolts 26" willpractically'never come outof the concrete center ll. 'I h'e blocirs l-fl cannot come out unlesslarge por-. tions of them break -ofi. This will rarely happen, but ifand when it 'do es the broken block or blocks can be readily replaced.As shown in Figure '1', I may provide blocks lli'a. with portions cutout which are of theshapeofabrasive plugs [41! one of; which isshowninperspective in Figure 2. The boltheads 21 have screw driver, slots-andthe bolts.

ZGTcan -be screwed outnfthe nuts\3"0. After the boltsrzfi. which heldthe broken block have been thus'removedthe washers 25 are inserted inthe ppcltetszll: of a block 'IUa, {the bolts -26 are passed"therethrouglh, the-block 'l 011- is placed inposition sea th bonerstightened] "Iihenfour pin-gs to areceniented in place and the .pulpstoneis .repaired.

From an examination of Figure 4, it will be noted that the bolts 26 canbe flexed a few thousandths of an inch before contacting the sleeves 28.This clearance prevents fracture of the bolts or of the blocks due toexpansion of the blocks or differential expansion between the blocks andthe stone. I I I .3 I

Tlie bonsai-may be made of {any suitable steel which is capable of beingput under tension Without permanently deforming. It is desirable thatthebolts 26 as well as the washers 25 be plated ""or i'iiade ofstainless steel in order that pulp water, which does-sometimes.penetratethe porous abrasive qnatriaLof t the blocks ll], shall not cause'theipulpstone to deteriorate by rusting of the bolts or wash ers. It isalso desirable that the seats ruetruedremakes smooth surface forengagementby the washers 25 or that washers of copper or other softmetal be provided between the washers and the seats 22. Alternatively,the washers 25 can be made of steel which is'soft enough to ecnrcrm tothejir'iegularitis of the seats 22.

Another preferred feature of the pulpstone is that the bases of theblocks m are preferably.

stronger than the grindingportions of the block's lB-.- B'y base? I meanthat area 'of'a'blo'ck which isinc'luded between the face l4 and thelevel "of the seats 22. The bases of the blocks do not at any time grindpulp and accordingly no considw erauon need b given to the a rasiveproperties of the bases. Iii-fact, the portions of the blocks which astne'grinamg constitute "the 'vdmme which is radiauy outward of the wasor the bolt heads 2'1. Th' e volur'ne of the blocks n the same: betweenthe top of the bolt heads '21 and the S'e at QZZ constitutes a sort ofintermediatezone which might be the same as "the outer abrasiveportion-of the block or the same composition as b e I l M It is knowniii the art how to make the bases of the block's strongerthan the outeror abrasive portions of theblocks. There are several different ways todo this but one means which is satisfa'J( :tor$ .co'ns ists in loadingthe lciwer' portion ofth mold which forms the block with abrasive ofsmaller grit size and possibly also providing a greater volumepercentagev of abrasive. Itis' the lower part of th'e rnolcl which formsthe base. I I Alternatively' 'the outer or, abrasive portions-of theblocks "I0", that is'to say,,btween the-surfaces ple, if fused aluminaabrasive of I24 grit size is mixed with clays, selecting quantities toprovide 4e volume per cent of abrasive and about 14.3

volume per cent of bond-,and to this is added enough coke in granuleform to make 15 volume per centin the pressed article, the coke being ofgrit size 12-14, there results a -suitable mixture for the abrasiveportionof the block which will have large pores, namely, from'grit size12 to grit size 14. If asecond mixture is made of the same abrasive ofthesa-me gri-t-size-and'the same bond, I but calculated to give volumeper cent of-abra siveand 15x5 volume per cent of bond, we have asuitable mixture for the base of the block which will resultingbase-much stronger than the abrasive portion of the block. These, twomixtures can 'be-simultaneously pressed to forman integralblock. Insteadof using cok e -to for-m the largepores, any other material which willbe eliminated during the burning of the-block may be used. An-

other example is naphthalene. I .Iihae s wnd a s ,;-.c@ i types t-pgrinding, a porous abrasive containing large pores, generally referredto as induced pores gives better performance. It isdesirable .in thisand other cases to form a.-.ba.se ppr-tion: of; thegblock fihich isstronger than theouter orabrasiv 13017;

Itwill be seen fromthe drawings that the seats 22 have a relatively widearea which is contacted by the washers 25." Thus a'large portion of ablockmustbreakbefore itcan come out of the pulpstone. Nor can the"blocks become loose due to contraction of the pulpstone because theyare held to the concrete center under tension and the forced s-exertedbetween,,the seats 22 andthe washers 29 ,via nuts 30. Yet despite this fthe only tightening operation'is d'one befor blocksare set in positionto formv the fstonT v }jI prefer to use washers 25 to fit'the seats2.2,"but alternativel large bolt heads might directly contact the-seats.Also While rprefer to place .the bolt heads 21 in the pocketsl ll andthe;,nuts an in the concrete, this arrangement might be re versed or twonuts might be used.

A special problem was involved in the formation of the pockets 20 andthe grooves 2|. Abrasive mixes in a mold behave somewhat as does a fluidbut they do not fully follow Pascal's laws. Such material under pressurewill form a reentrant angle in the piece if the mold is so shaped, butthere are limits to the amount of material which may be pressed aroundcorners without forming cracks in the fired article. I have found thataccurate pockets 20 and grooves 2| with good seats 22 can be formed byproceeding as follows:

Provide a pair of knurled spindles of a diameter barely less than thewidth of the groove 2| and on the ends thereof afllx abrasive wheels orline toothed milling cutters. Space these apart the distance betweenpockets, etc., on parallel axes. Mount a green (before firing) block H!on a slide and move it slowly against the wheels or cutters andspindles. The wheels or cutters form the pockets 2|! while the spindlesform the grooves 2|. Uniform fiat seats 22 are formed in this way.

Although the drawings show but one ring of blocks it is intended thatseveral rings be superimposed upon each other to form a pulpstone whichhas a plurality of blocks across its face i. e. in an axial direction.The marginal blocks preferably have one side which is straight, that isin a true radial plane. No illustration of these features was madebecause per se they are old in the art.

It will thus be seen that there has been provided by this invention anarticle in which the various objects hereinabove set. forth togetherwith many thoroughly practical advantages are successfully achieved. Asvarious possible em-- bodiments might be made of the mechanical featuresof the above invention and as the art herein described might be variedin various parts, all without departing from the scope of the invention,it is to be understood that all matter hereinbefore set forth or shownin the accompanying drawings is to be interpreted as illustrative andnot in a limiting sense.

I claim:

1. A pulpstone or the like comprising a concrete center of annularshape, a plurality of blocks of bonded abrasive material on the outsideof said center to form an abrasive annulus, each block having an outerabrading surface, an inner surface adjacent the center, and a pluralityof faces between said surfaces, each block having a pocket in each oftwo faces forming a seat at the bottom thereof, there being a groove inthe block extending from each pocket to-the inner surface of the ,blocka, bar-across, the inner.-sur-. face of the blockextending between saidgrooves, a sleeve against each end of thebarsand extend ing into the"concrete center, bolts inthe sleeves and extending beyond the sleevesand intoithe pockets,,and-means on eachendof the bolts both in: thepockets, and embedded in the concrete,said meansholding the belts intension and the sleeves under-compression, and .tlratportion of the.blocks radially inward of -the seats being und er compreS; sion derivedfrom the ,bolts and exertedagainst the seats. 2'. Apulpstone orthe likeas claimed in claim 1 wherein the outer portions of the blocks, radiallyou war r l v f t e wa of ..m kei s of desired abrasive characteristics,and manne portion of. the blocks. radially inward from. (the seats,- isoflstronger composition regardlesso its abrasive characteristics 1 yetvthe blocks: are inf tegral pieces.

3. A pulpstone or the like as claimed in claim 1 in which at least someof the blocks are keyed to the concrete including a projection in onepart fitting a recess in the other part.

4. A pulpstone or the like comprising a concrete center of annularshape, a plurality of blocks of bonded abrasive material on the outsideof said center to form an abrasive annulus, bolts in the blocks and inthe center holding the blocks to the said center, some of the blockshaving portions cut out radially outward from the bolts whereby saidbolts have been inserted through said out out portions to secure saidblocks to said center, and abrasive plugs inserted in said out outportions.

5. A pulpstone or the like comprising a concrete center of annularshape, a plurality of blocks of bonded abrasive material on the outsideof said center to form an abrasive annulus, each block having an outerabrading surface, an inner surface adjacent the center, and a pluralityof faces between said surfaces, each block having pockets in each of twofaces forming a seat at the bottom thereof, there being a groove in theblock extending from each pocket to the inner surface of the block, barsacross the inner surface of the block extending between said grooves, asleeve against each end of the bars and extending into the concretecenter, bolts in the sleeves and extending beyond the sleeves and intothe pockets, and means on each end of the bolts both in the pockets andembedded in the concrete, said means holding the bolts in tension andthe sleeves under compression, and that portion of the blocks radiallyinward of the seats being under compression derived from the bolts andexerted against the seats.

6. A pulpstone or the like comprising a concrete center of annularshape, a plurality of blocks of bonded abrasive material on the outsideof said center to form an abrasive annulus, each block having an outerabrading surface, an inner surface adjacent the center, and a pluralityof faces between said surfaces, each block having pockets in one faceand opposing pockets in an opposite face forming seats at the bottomsthereof, there being a groove in the block extending from each pocket tothe inner surface of the block, bars across the inner surface of theblock extending between the grooves of said opposing pockets, a sleeveagainst each end of the bars and extending into the concrete center,bolts in the sleeves and extending beyond the sleeves and into thepockets, and means on each end of the bolts both on

